Welcome to SMF I hope you find your time here knowledgeable and enjoyable, lots of info and good people ready to help so that your smoking experience is pleasurable.
For your question, I bought a Sentry valve but never used it because it was intended to sense temps in a liquid environment and not a dry one like is found in our smokers. I read on your other post you have a Perfect Flame Smoker, correct me if I'm wrong, but that is a propane fired unit isn't it?
1. Are you having problems holding a set temperature?
2. Is your flame blue with just the tips orange.
3. When turning the control knob and watching the burner does the flame become longer when you go from lo to hi?
4. When you set it at, let's say med, is the flame different than when you are set at lo or hi?
5. Do you turn the tank regulator on with the smoker regulator closed, if not there is a safety device that limits the amount of flow from the tank, that could be your problem.
Get back to us and we can go from there with advice.
I hope that helps.